Bidentate Disilicate Framework for Bis‐Grafted Surface Species

Abstract

Recent advances in surface organometallic chemistry have enabled the detailed characterization of the surface species in single‐site heterogeneous catalysts. However, the selective formation of bis‐grafted surface species remains challenging because of the heterogeneity of the supporting surface. Herein, we introduce a metal complex bearing bidentate disilicate ligands, −OSi(OtBu)2OSi(OtBu)2O−, as a molecular precursor, which has a silicate framework adjacent to the metal (Pt) center. The grafting of the precursors on silica supports (MCM‐41 and CARiACT Q10) proceeded through a substitution reaction on the silicon atoms of the disilicate ligand, which was verified by the detection of isobutene and tBuOH as the elimination products, to selectively yield bis‐grafted surface species. The chemical structure of the surface species was characterized by solid‐state NMR, and the chemical shift values of the ancillary ligands and 195Pt nuclei suggested that the bidentate coordination sphere was maintained following grafting.

Enhanced Catalysis Based on the Surface Environment of the Silica-Supported Metal Complex

“…For example, the structure and catalytic activity of surface La sites could be controlled by the density of silanol, resulting in a uniform active species . Regarding a novel grafting technique, Choi and co-workers recently reported the use of bidentate disilicate framework for the selective production of a specific surface Pt complex . The catalytic performance often significantly increased by the site-isolation/cooperative catalysis design; however, unfortunately, especially in the case of bifucntional catalytic surface, it is not easy to control the distance between two different functionalities precisely.…”

“…273 Regarding a novel grafting technique, Choi and co-workers recently reported the use of bidentate disilicate framework for the selective production of a specific surface Pt complex. 278 The catalytic performance often significantly increased by the site-isolation/cooperative catalysis design; however, unfortunately, especially in the case of bifucntional catalytic surface, it is not easy to control the distance between two different functionalities precisely. The use of a weak interaction in the precursor solution including both of active species is one of the potential solutions to control their cooperativity.…”

Molecular and Electronic Structure of Isolated Platinum Sites Enabled by the Expedient Measurement of195Pt Chemical Shift Anisotropy

“…However, direct NMR experiments on the metal nucleus of supported catalysts are challenging because of the typically low metal loadings. Consequently, NMR experiments have traditionally been limited to highly receptive isotopes of metals such as aluminum, scandium, vanadium, , niobium, and/or isotopically enriched materials. ,, Recently, sensitivity-enhancement by dynamic nuclear polarization (DNP) or proton detection has enabled NMR experiments on catalysts featuring unreceptive nuclei. − …”

Multinuclear rhodium complexes supported by tetra-tert-butoxy disiloxide ligand: synthesis, structure, and reactivity

“…45 We have recently developed a platinum complex supported by a bidentate tetra-tert-butoxy disiloxide ligand, [(OSi(O t Bu) 2 ) 2 O], in which neither self-condensation nor siloxane disproportionation was observed (Scheme 1c). 46,47 Herein, we used a bidentate disiloxide ligand to synthesize rhodium complexes and elucidate their structure in solution and solid states and their reactivity toward carbon monoxide and trimethylphosphine (Scheme 1d).…”